1. Field of the Invention
The present invention relates to a peropyrene compound suitable as a luminescent material for an organic electroluminescent element, an organic electroluminescent element using the peropyrene compound, and an organic electroluminescent display using the organic electroluminescent element.
2. Description of the Related Art
Organic electroluminescent elements have features such as self-luminescence and high-speed response and their application for flat panel displays are expected. In particular, two-layer (multilayered) organic electroluminescent elements receive attention as large-area luminescent elements capable of emitting light at low voltages of 10 V or less. Such multilayered organic electroluminescent elements each comprise a hole-transporting organic thin film (hole-transporting layer) and an electron-transporting organic thin film (electron-transporting layer) and have been reported typically in C. W. Tang and S. A. VanSlyke, Applied Physics Letters vol. 51, 913 (1987). Such multilayered organic electroluminescent elements basically have a basic configuration of positive electrode/hole-transporting layer/light-emitting layer/electron-transporting layer/negative electrode, in which the hole-transporting layer or the electron-transporting layer may also serve as the light-emitting layer as in the two-layer organic electroluminescent element.
The application of organic electroluminescent elements for a full-color display have been expected. In the full-color display, pixels showing three primary colors, i.e., blue (B), green (G) and red (R), must be arranged on a panel. Proposed methods for arranging the pixels are (a) a method of arranging three different organic electroluminescent elements emitting blue (B), green (G) and red (R) light, respectively; (b) a method of separating white light (color mixture of blue (B), green (G) and red (R) light) emitted from a white-light-emitting organic electroluminescent element into the three primary colors using a color filter; and (c) a method of converting blue light from a blue-light-emitting organic electroluminescent element into green (G) light and red (R) light with the use of a color conversion layer utilizing fluorescence emission.
A technique for yielding an organic electroluminescent element having a high emission efficiency is proposed in, for example, C. W. Tang, S. A. VanSlyke, and C. H. Chen, Journal of Applied Physics vol. 65, 3610 (1989). According to this technique, a host material serving as a main material is doped with a small amount of a dye molecule capable of highly emitting fluorescence as a guest material to form a light-emitting layer exhibiting a high emission efficiency.
These conventional organic electroluminescent elements, in particular those for emitting red light, however, are still insufficient in emission efficiency (for example, Japanese Patent Application Laid-Open (JP-A) No. 2000-231987) and demands have been made to develop novel and high-performance organic electroluminescent elements.
Accordingly, an object of the present invention is to solve the problems in conventional technologies and to provide a peropyrene compound suitable as a red-light emitting material in an organic electroluminescent element and to provide an organic electroluminescent element which is excellent typically in emission efficiency, emission luminance and color purity of red light. Another object of the present invention is to provide a high-performance organic electroluminescent display using the organic electroluminescent element.
After intensive investigations to achieve the above objects, the present inventors have obtained the following findings. Specifically, they have found that a specific peropyrene compound is suitable as a red-light emitting material in an organic electroluminescent element, and that an organic electroluminescent element and an organic electroluminescent display each using the peropyrene compound as a luminescent material are excellent typically in emission efficiency, emission luminance and color purity of red light and exhibit higher performance than conventional equivalents.